The following discussion proceeds with the exemplary petroleum-based material of asphalt, although it is to be understood that other petroleum-based, petroleum-containing and organic materials exist which are either desirous of being recycled or in certain instances, desirous of being mined and abstracted from their native and virgin environment. Accordingly, the present invention contemplates and includes all such petroleum-based, petroleum-containing and other organic materials within its scope.
Asphalt is a universal raw material used for roadways, parking lots and other surface treatments. The asphalt material is generally a composition of minerals including aggregate and sand or stone dust and an asphalt binder. Additionally, novel asphalt mixtures include various substitutes for the aggregate (coarse and fine) including: crushed glass, used tires, and other reclaimed materials. The asphalt binder is basically the glue that binds the mineral or aggregate ingredients such that they are solid under normal operating or environmental temperatures but semi-liquid under elevated temperatures. Another product related to the commonly known term as asphalt is roofing shingles, composed of similar components including aggregate, asphalt binder, and fiberglass.
A typical asphalt composition contains a general ratio of materials as follows: coarse aggregate including crushed minerals or stone having particle sizes in the range from about ⅜ to 1 inch, or 70-85% of volume, fine aggregate including compositions of crushed stone dust, crushed glass, sand or other small sized filler, or 10-20% of volume, asphalt binder, a blend of petroleum refinery product (byproduct) that can be further modified to achieve certain asphalt mixtures or grades, about 10% by volume, and miscellaneous ingredients including trapped air (voids) and moisture. A typical asphalt mixture is the blending of the coarse and fine aggregate with the asphalt binder. However, in the blending process, some trapped air is normally also included. The amount of trapped air and the coating and bonding of the asphalt binder to the aggregate determines the quality and grade of the final asphalt product. As these materials are mixed, the asphalt composition is subjected to elevated temperature (about 300-400° F.) and uniformly mixed such that a uniform blending of components is achieved. This hot mixture is bonded by the phase change of the asphalt binder from a semi-liquid to a solid. As the semi-liquid asphalt binder coats the coarse and fine aggregates, the final asphalt mixture is blended to meet the requirements of the needed final product.
Certain asphalt mixtures are required to meet Department of Transportation specifications based upon application location, environmental and temperature ranges and other requirements. The various grades of asphalt are based upon the aggregate size (coarse and fine), content and percentages of the added components including binder. These asphalt grades created by their respective asphalt binders, screened aggregate particle sizes, compaction forces on the mixture and vibratory rolling to further orientate the final asphalt composition prior to solidification.
As the asphalt is applied to a surface and rolled so that the final flat surface is achieved, other variables are introduced that can affect asphalt quality. These variables or conditions include surface temperatures, asphalt temperatures, application thicknesses and other application variables that may affect the final grade of the asphalt achieved. The asphalt binder applied is a form of thermoplastic that solidifies as the temperature is reduced from the asphalt blending temperature (300-400° F.) to the final product application temperatures (−60 to 160° F.). These temperature ranges affect the temperature change rate or thermal gradient of the solidification process and this affects the final product compaction ratio, density and mechanical properties. The final asphalt product performance factors are based upon these components, the mixture ratios and application methods.
The asphalt binder is phase changed from a solid at ambient temperatures to a semi liquid at elevated temperatures (a plastic state or high viscosity state) that coats the coarse and fine aggregates and fills the voids of the mixture. Aggregate uniformity coating issues occur with the semi liquid asphalt binder because it cannot be thoroughly liquid. After a certain elevation in temperature, the asphalt binder burns or degrades. This asphalt binder aggregate coating capability is an important aspect of achieving higher grade asphalts. It would be desirable to coat the aggregate in an improved manner.
Once an asphalt mixture is applied and rolled onto a desired surface (roadway, parking lot driveway, etc.), the lower temperature of the contact surface changes the asphalt binder back from a semi-liquid state to a solid. This becomes the desired asphalt final product. The coarse and fine aggregate compositions, mixture ratios and asphalt binder blends may further improve the asphalt mixture and final asphalt product properties that may provide an improved life cycle, operating temperature exposure characteristics, weight load bearing properties, surface coefficient of friction characteristics and other desired properties.
The current methods for recycling asphalt typically take certain percentages of “millings” or scrapped/salvaged asphalt from an existing, aged or degraded asphalt surface and blend a small percentage of these millings into a virgin mixture of asphalt (a blend of 25% millings to 75% virgin asphalt is a normal practice). These recycling methods provide a means of recovering small percentages of the “used” or “salvaged” asphalt for recycling back into a new asphalt. As a general rule, approximately 10-30% of millings can remixed with virgin asphalt. This is because the new asphalt mixture is degraded with the addition of aged millings because it does not blend as uniformly as virgin materials. This practice is not allowed in some jurisdictions (approximately 22 States have banned this process) because the new asphalt mixture (with the recycled asphalt content) is inferior. This is likely the result of the aged asphalt having asphalt binder in a crystalline or solid state that cannot phase change or liquefy as the virgin asphalt binder and thus cannot completely blend into the mixture. This yields a lower grade asphalt mixture that has limited use such applications as parking lots and driveways.
Elseifi et al., U.S. Patent Publication 2014/0299018 teach a process for separating constituents of an asphalt-based material including at least asphalt and one solid non-asphalt material by shredding the asphalt-based material to form a shredded material mass. Next, an asphalt binder at an elevated temperature is added to absorb the recoverable asphalt binder from the shredded material. This produces a 30-40% increase in the binder volume, i.e. the recovered binder from the shredded material.
Kotefski et al., U.S. Ser. No. 15/355,487, filed Nov. 18, 2016, the disclosure of which is herein incorporated by reference, teach methods to reclaim or recycle asphalt or asphalt components to produce reusable asphalt or asphalt components by adding the asphalt or asphalt components to a solution at a temperature higher than the melting temperature of the asphalt binder. The solution may be at least 300° F., 325° F., 350° F. or 400° F. or so, and the solution may be an oil or petroleum based solution or any other suitable solution in which the asphalt binder is soluble. In some instances, the solution may be virgin motor oil or recycled motor oil. It is desirable to provide new and improved methods to reclaim or recycle asphalt to produce reusable asphalt and asphalt components. Preferably, reusable asphalt and asphalt components that have the physical properties of virgin asphalt.
It is also desirable to provide further improved methods to reclaim or recycle asphalt or asphalt components to produce reusable asphalt or asphalt components, petroleum-based, petroleum-containing, and organic materials that are either desirous of being recycled or in certain instances, desirous of being mined and abstracted from their native or virgin environment, organic materials, collectively referred to herein as petroleum-based material.